////////////////////////////////////////////////////////////////////////////// | |
// | |
// (C) Copyright Ion Gaztanaga 2005-2009. Distributed under the Boost | |
// Software License, Version 1.0. (See accompanying file | |
// LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt) | |
// | |
// See http://www.boost.org/libs/interprocess for documentation. | |
// | |
////////////////////////////////////////////////////////////////////////////// | |
// | |
// This interface is inspired by Howard Hinnant's lock proposal. | |
// http://home.twcny.rr.com/hinnant/cpp_extensions/threads_move.html | |
// | |
////////////////////////////////////////////////////////////////////////////// | |
#ifndef BOOST_INTERPROCESS_UPGRADABLE_LOCK_HPP | |
#define BOOST_INTERPROCESS_UPGRADABLE_LOCK_HPP | |
#if (defined _MSC_VER) && (_MSC_VER >= 1200) | |
# pragma once | |
#endif | |
#include <boost/interprocess/detail/config_begin.hpp> | |
#include <boost/interprocess/detail/workaround.hpp> | |
#include <boost/interprocess/interprocess_fwd.hpp> | |
#include <boost/interprocess/sync/lock_options.hpp> | |
#include <boost/interprocess/detail/mpl.hpp> | |
#include <boost/interprocess/detail/type_traits.hpp> | |
#include <boost/interprocess/exceptions.hpp> | |
#include <boost/interprocess/detail/move.hpp> | |
#include <boost/interprocess/detail/posix_time_types_wrk.hpp> | |
//!\file | |
//!Describes the upgradable_lock class that serves to acquire the upgradable | |
//!lock of a mutex. | |
namespace boost { | |
namespace interprocess { | |
//!upgradable_lock is meant to carry out the tasks for read-locking, unlocking, | |
//!try-read-locking and timed-read-locking (recursive or not) for the Mutex. | |
//!Additionally the upgradable_lock can transfer ownership to a scoped_lock | |
//!using transfer_lock syntax. The Mutex need not supply all of the functionality. | |
//!If the client of upgradable_lock<Mutex> does not use functionality which the | |
//!Mutex does not supply, no harm is done. Mutex ownership can be shared among | |
//!read_locks, and a single upgradable_lock. upgradable_lock does not support | |
//!copy semantics. However upgradable_lock supports ownership transfer from | |
//!a upgradable_locks or scoped_locks via transfer_lock syntax. | |
template <class UpgradableMutex> | |
class upgradable_lock | |
{ | |
public: | |
typedef UpgradableMutex mutex_type; | |
/// @cond | |
private: | |
typedef upgradable_lock<UpgradableMutex> this_type; | |
explicit upgradable_lock(scoped_lock<mutex_type>&); | |
typedef bool this_type::*unspecified_bool_type; | |
BOOST_INTERPROCESS_MOVABLE_BUT_NOT_COPYABLE(upgradable_lock) | |
/// @endcond | |
public: | |
//!Effects: Default constructs a upgradable_lock. | |
//!Postconditions: owns() == false and mutex() == 0. | |
upgradable_lock() | |
: mp_mutex(0), m_locked(false) | |
{} | |
explicit upgradable_lock(mutex_type& m) | |
: mp_mutex(&m), m_locked(false) | |
{ mp_mutex->lock_upgradable(); m_locked = true; } | |
//!Postconditions: owns() == false, and mutex() == &m. | |
//!Notes: The constructor will not take ownership of the mutex. There is no effect | |
//! required on the referenced mutex. | |
upgradable_lock(mutex_type& m, defer_lock_type) | |
: mp_mutex(&m), m_locked(false) | |
{} | |
//!Postconditions: owns() == true, and mutex() == &m. | |
//!Notes: The constructor will suppose that the mutex is already upgradable | |
//! locked. There is no effect required on the referenced mutex. | |
upgradable_lock(mutex_type& m, accept_ownership_type) | |
: mp_mutex(&m), m_locked(true) | |
{} | |
//!Effects: m.try_lock_upgradable(). | |
//!Postconditions: mutex() == &m. owns() == the return value of the | |
//! m.try_lock_upgradable() executed within the constructor. | |
//!Notes: The constructor will take upgradable-ownership of the mutex | |
//! if it can do so without waiting. Whether or not this constructor | |
//! handles recursive locking depends upon the mutex. If the mutex_type | |
//! does not support try_lock_upgradable, this constructor will fail at | |
//! compile time if instantiated, but otherwise have no effect. | |
upgradable_lock(mutex_type& m, try_to_lock_type) | |
: mp_mutex(&m), m_locked(false) | |
{ m_locked = mp_mutex->try_lock_upgradable(); } | |
//!Effects: m.timed_lock_upgradable(abs_time) | |
//!Postconditions: mutex() == &m. owns() == the return value of the | |
//! m.timed_lock_upgradable() executed within the constructor. | |
//!Notes: The constructor will take upgradable-ownership of the mutex if it | |
//! can do so within the time specified. Whether or not this constructor | |
//! handles recursive locking depends upon the mutex. If the mutex_type | |
//! does not support timed_lock_upgradable, this constructor will fail | |
//! at compile time if instantiated, but otherwise have no effect. | |
upgradable_lock(mutex_type& m, const boost::posix_time::ptime& abs_time) | |
: mp_mutex(&m), m_locked(false) | |
{ m_locked = mp_mutex->timed_lock_upgradable(abs_time); } | |
//!Effects: No effects on the underlying mutex. | |
//!Postconditions: mutex() == the value upgr.mutex() had before the | |
//! construction. upgr.mutex() == 0. owns() == upgr.owns() before the | |
//! construction. upgr.owns() == false. | |
//!Notes: If upgr is locked, this constructor will lock this upgradable_lock | |
//! while unlocking upgr. If upgr is unlocked, then this upgradable_lock will | |
//! be unlocked as well. Only a moved upgradable_lock's will match this | |
//! signature. An non-moved upgradable_lock can be moved with the | |
//! expression: "boost::interprocess::move(lock);". This constructor does not alter the | |
//! state of the mutex, only potentially who owns it. | |
upgradable_lock(BOOST_INTERPROCESS_RV_REF(upgradable_lock<mutex_type>) upgr) | |
: mp_mutex(0), m_locked(upgr.owns()) | |
{ mp_mutex = upgr.release(); } | |
//!Effects: If scop.owns(), m_.unlock_and_lock_upgradable(). | |
//!Postconditions: mutex() == the value scop.mutex() had before the construction. | |
//! scop.mutex() == 0. owns() == scop.owns() before the constructor. After the | |
//! construction, scop.owns() == false. | |
//!Notes: If scop is locked, this constructor will transfer the exclusive-ownership | |
//! to an upgradable-ownership of this upgradable_lock. | |
//! Only a moved sharable_lock's will match this | |
//! signature. An non-moved sharable_lock can be moved with the | |
//! expression: "boost::interprocess::move(lock);". | |
template<class T> | |
upgradable_lock(BOOST_INTERPROCESS_RV_REF(scoped_lock<T>) scop | |
, typename detail::enable_if< detail::is_same<T, UpgradableMutex> >::type * = 0) | |
: mp_mutex(0), m_locked(false) | |
{ | |
scoped_lock<mutex_type> &u_lock = scop; | |
if(u_lock.owns()){ | |
u_lock.mutex()->unlock_and_lock_upgradable(); | |
m_locked = true; | |
} | |
mp_mutex = u_lock.release(); | |
} | |
//!Effects: If shar.owns() then calls try_unlock_sharable_and_lock_upgradable() | |
//! on the referenced mutex. | |
//! a)if try_unlock_sharable_and_lock_upgradable() returns true then mutex() | |
//! obtains the value from shar.release() and owns() is set to true. | |
//! b)if try_unlock_sharable_and_lock_upgradable() returns false then shar is | |
//! unaffected and this upgradable_lock construction has the same | |
//! effects as a default construction. | |
//! c)Else shar.owns() is false. mutex() obtains the value from shar.release() | |
//! and owns() is set to false. | |
//!Notes: This construction will not block. It will try to obtain mutex | |
//! ownership from shar immediately, while changing the lock type from a | |
//! "read lock" to an "upgradable lock". If the "read lock" isn't held | |
//! in the first place, the mutex merely changes type to an unlocked | |
//! "upgradable lock". If the "read lock" is held, then mutex transfer | |
//! occurs only if it can do so in a non-blocking manner. | |
template<class T> | |
upgradable_lock( BOOST_INTERPROCESS_RV_REF(sharable_lock<T>) shar, try_to_lock_type | |
, typename detail::enable_if< detail::is_same<T, UpgradableMutex> >::type * = 0) | |
: mp_mutex(0), m_locked(false) | |
{ | |
sharable_lock<mutex_type> &s_lock = shar; | |
if(s_lock.owns()){ | |
if((m_locked = s_lock.mutex()->try_unlock_sharable_and_lock_upgradable()) == true){ | |
mp_mutex = s_lock.release(); | |
} | |
} | |
else{ | |
s_lock.release(); | |
} | |
} | |
//!Effects: if (owns()) m_->unlock_upgradable(). | |
//!Notes: The destructor behavior ensures that the mutex lock is not leaked. | |
~upgradable_lock() | |
{ | |
try{ | |
if(m_locked && mp_mutex) mp_mutex->unlock_upgradable(); | |
} | |
catch(...){} | |
} | |
//!Effects: If owns(), then unlock_upgradable() is called on mutex(). | |
//! *this gets the state of upgr and upgr gets set to a default constructed state. | |
//!Notes: With a recursive mutex it is possible that both this and upgr own the | |
//! mutex before the assignment. In this case, this will own the mutex | |
//! after the assignment (and upgr will not), but the mutex's upgradable lock | |
//! count will be decremented by one. | |
upgradable_lock &operator=(BOOST_INTERPROCESS_RV_REF(upgradable_lock) upgr) | |
{ | |
if(this->owns()) | |
this->unlock(); | |
m_locked = upgr.owns(); | |
mp_mutex = upgr.release(); | |
return *this; | |
} | |
//!Effects: If mutex() == 0 or if already locked, throws a lock_exception() | |
//! exception. Calls lock_upgradable() on the referenced mutex. | |
//!Postconditions: owns() == true. | |
//!Notes: The sharable_lock changes from a state of not owning the mutex, | |
//! to owning the mutex, blocking if necessary. | |
void lock() | |
{ | |
if(!mp_mutex || m_locked) | |
throw lock_exception(); | |
mp_mutex->lock_upgradable(); | |
m_locked = true; | |
} | |
//!Effects: If mutex() == 0 or if already locked, throws a lock_exception() | |
//! exception. Calls try_lock_upgradable() on the referenced mutex. | |
//!Postconditions: owns() == the value returned from | |
//! mutex()->try_lock_upgradable(). | |
//!Notes: The upgradable_lock changes from a state of not owning the mutex, | |
//! to owning the mutex, but only if blocking was not required. If the | |
//! mutex_type does not support try_lock_upgradable(), this function will | |
//! fail at compile time if instantiated, but otherwise have no effect. | |
bool try_lock() | |
{ | |
if(!mp_mutex || m_locked) | |
throw lock_exception(); | |
m_locked = mp_mutex->try_lock_upgradable(); | |
return m_locked; | |
} | |
//!Effects: If mutex() == 0 or if already locked, throws a lock_exception() | |
//! exception. Calls timed_lock_upgradable(abs_time) on the referenced mutex. | |
//!Postconditions: owns() == the value returned from | |
//! mutex()->timed_lock_upgradable(abs_time). | |
//!Notes: The upgradable_lock changes from a state of not owning the mutex, | |
//! to owning the mutex, but only if it can obtain ownership within the | |
//! specified time. If the mutex_type does not support | |
//! timed_lock_upgradable(abs_time), this function will fail at compile | |
//! time if instantiated, but otherwise have no effect. | |
bool timed_lock(const boost::posix_time::ptime& abs_time) | |
{ | |
if(!mp_mutex || m_locked) | |
throw lock_exception(); | |
m_locked = mp_mutex->timed_lock_upgradable(abs_time); | |
return m_locked; | |
} | |
//!Effects: If mutex() == 0 or if not locked, throws a lock_exception() | |
//! exception. Calls unlock_upgradable() on the referenced mutex. | |
//!Postconditions: owns() == false. | |
//!Notes: The upgradable_lock changes from a state of owning the mutex, | |
//! to not owning the mutex. | |
void unlock() | |
{ | |
if(!mp_mutex || !m_locked) | |
throw lock_exception(); | |
mp_mutex->unlock_upgradable(); | |
m_locked = false; | |
} | |
//!Effects: Returns true if this scoped_lock has acquired the | |
//!referenced mutex. | |
bool owns() const | |
{ return m_locked && mp_mutex; } | |
//!Conversion to bool. | |
//!Returns owns(). | |
operator unspecified_bool_type() const | |
{ return m_locked? &this_type::m_locked : 0; } | |
//!Effects: Returns a pointer to the referenced mutex, or 0 if | |
//!there is no mutex to reference. | |
mutex_type* mutex() const | |
{ return mp_mutex; } | |
//!Effects: Returns a pointer to the referenced mutex, or 0 if there is no | |
//! mutex to reference. | |
//!Postconditions: mutex() == 0 and owns() == false. | |
mutex_type* release() | |
{ | |
mutex_type *mut = mp_mutex; | |
mp_mutex = 0; | |
m_locked = false; | |
return mut; | |
} | |
//!Effects: Swaps state with moved lock. | |
//!Throws: Nothing. | |
void swap(upgradable_lock<mutex_type> &other) | |
{ | |
std::swap(mp_mutex, other.mp_mutex); | |
std::swap(m_locked, other.m_locked); | |
} | |
/// @cond | |
private: | |
mutex_type *mp_mutex; | |
bool m_locked; | |
/// @endcond | |
}; | |
} // namespace interprocess | |
} // namespace boost | |
#include <boost/interprocess/detail/config_end.hpp> | |
#endif // BOOST_INTERPROCESS_UPGRADABLE_LOCK_HPP |